Boiler with high evaporative capacity



March 17, 1931 DHQME I 1,796,512

BOILER WITH HIGH EVAPORATIVE CAPACITY 7 Filed Dec. 3, 1926 2 Sheets-Sheet 1 mveumn March 17, 1931. A. DHOME 1,796,512

BOILER WITH HIGH EVAPORATIVE CAPACITY I Filed Dec. 5, 192a 2 Sheets-Sheet v 2 Fig.

Patented Mar. 17, 1931 UNITED STATES PATENT GF'FICE ALFRED DI-IOME, OF ST.DENIS, FRANCE, ASSIGNOR TO SOGIETE ANONYME IDES ETAB- LISSEMENTS DELAUNAY IBELLEVILLE, OF SI.DENIS, FRANCE, A FRENCH CORPO- RATION BOILER WITH HIGH EVAlORATIVE CAPACITY Application filed December 3, 1926, Serial N 0. 152,435, and in France December 17, 1925.

The present invention relates to water tube boilers and more particularly to a type of water tube steam boiler, which allows of obtaining very high rates of evaporation with great security, and is constituted by evaporative tubes provided with gills or ribs, said gills being more numerous and spaced more closely together as the tubes are more and more distant from the furnace and one series of the tube elements of the boiler being so located as to afford efiicient protection to the refractory walls of the furnace.

It is known that the transmission of they heat of the combustion gases to the water in boilers is effected in three stages.

1. From the gases to the metal of the heating surface.

2. Through the metal.

3. From the metal to the water to be evaporated.

The transmissions 2 and 3 take place easily, owing to high coefiicients. It is only the transmission 1, that is from the gases to the metal, which is diii'icult, the heat exchange coefficient being low.

In ordinary water tube boilers there is active transmission of heat primarily through the surfaces directly exposed to radiation from the furnace and secondarily through the material of the first rows of tubes, in respect'of which the high temperature of the gases compensates for the lowness of the coefficient of transmission by convection. Evaporation subsequently diminishes quickly and in order to cool down the combustion gases sufliciently before they are discharged, it is necessary to make them pass through a great number of rows of tubes. A fair result can only be obtained by means of certain devices, particularly'by means of battles constraining the gases to make several passages through the nest of tubes. Anyhow only a small increase is obtained of the mean rate of evaporation of the boiler andat the expense of a great increase in the activity of the first rows of tubes. 7

The boiler, which is the subject of the present invention, obtains high rates of evaporation owing to an improved distribution of heat absorbed by the various tubes. it has at the same time a high eflic1ency at the most diverse temperatures owlng to the efficiency in the absorption of the heat of with the drum 1, each element being constituted by two straight headers 2, to which are attached the evaporative tubes 3 by expanding, welding or any other method.

The evaporative tubes 3, or at least a part of them, are provided with metal gills, projections or ribs 4; made when casting or machining or attached by welding or any other means giving an intimate connection of the metal. The purpose of these ribs is to increase the metallic surface in contact with the gases, and thus to obtain a greater heat transmission than with the same tubes without ribs. By increasing the number and size of the gills in proportion to the cooling down of the gases it is possible to maintain a high rate of evaporation up to the last rows of tubes and nevertheless to obtain a very low discharge temperature of the gases, that is to say a high efiiciency for the boiler.

Communicating tubes 5 connect the headers 2 with'the drum 1 and permit the circulation of the water and the giving ofi of the steam. The headers 52 of the elements are if necessary slightly machined on their contact surfaces in order to obtain sealing for the gases.

A feed and depositing drum 6 connected with each element is also provided and allows of the easy removal of deposits and mud at the same time as a practical feed.

The great efficiency of the transmission obtained enables several interesting arrangements to be realized. In the first place, it can be arranged that the gases traverse only a reduced number of rows of tubes, in consequence baiiles may be dispensed with and only a single passage for the gases is thus left. T he elimination of balies allows of the easy installation of powe ful cleaning apparatus the utility of which is well known.

In the second place such a boiler with a direct path for the gases and a small nu nl r of rows of tubes offers very little resistance to the passage or the This allows of high speed of circulation, which are themselves favourable to the transmission o heat.

Finally the headers 2 of one and the same element may be arranged at an angle to each other thus allowing of maintaining high ates of passage for the gases, in spite of their cooling down. This arrangement \v uld have furthermore the advantage of shortening the comnn'inicating pipes and of thus facilitating a good circulation in the boiler. The speed of the can also be increased by bringing the tubes nearer together.

This type of boiler may also comprise two or more drums 1 if it ished to increase the reserve of water. lVith this object evaporative tubes 3 of comparatively large diameter can be used whilst maintaining a high rate of evaporation Furthermore, several series of headers 2 can be attached to the drums 1. One of the additional series of headers can be utilized to protect the furnace walls, whilst at the same time the corresponding evaporative tubes can serve for increasing the activity of the boiler. For this purpose it is sufficient to place the evaporative tubes in question in communication with the drum 1 and to distribute them at the desired level by causing them to pass in front of the refractory walls or inside them in order to protect them from the action of the fire.

By way of example there are shown in Fig. 8 the position of the additional head- -rs 2 and tubes 3 protecting the walls, the normal elements of the boiler being constituted by the headers 2 and tubes 3 shown in full lines. The tubes 3 may be smooth or also provided with ribs or gills. Pipes 5 connect the headers 2, 3 with the drum 1 thereby placing the evaporative tubes in communication with the drum independently of the tubes 3.

Claim:

A water tube boiler with high evaporative capacity, comprising in combination substantially parallel evaporation tubes arranged in pa 'allel groups, headers connected to the ends of said tubes, arranged parallel to the general flow of gases escaping from the furnace, an upper drum connected to said headers, the headers to which are connected the ends of the tubes converging so ture.

ALFRED DHOME. 

